Thanks - although very simple and sturdy but they work, thanks to things behind the scenes - for those interested in aperture sights, here are some things worth look at.

- Theory from Lyman:

http://www.lymanproducts.com/lyman/sights/pdf/LyC_Sight_Tang.pdf

- Parallax suppresion with a target rifle aperture sight by A. Kerr - interesting stuff that explains a lot:

http://dougkerr.net/Pumpkin/articles/Aperture_Sight_Demo.pdf

- How things work out in praxis - I found it somewhere on the net but forgot where and who wrote it, but it is as it says:

"Step 1
Look through your peep sight at a bright wall or the sky (on a non-cloudy day). Do NOT allow the front sight to come into view. Do you see the small "fuzzy" in the middle of the rear sight? Some people see it as a blur, others see a gray or a blue-gray object. This "fuzzy" is the OPTICAL CENTER of your rear sight.

Step 2
Add the front sight to your view. Notice how your eye automatically put the tip of the front sight into the middle of the "fuzzy"? Your eye likes having things lined up (the optical center of the rear sight is now aligned with the front sight).

Step 3
Let's add a target into your sight picture. Again, you'll notice that your eye has automatically put the target into the optical center of the rear sight and at the tip of the front sight. By now your eye is getting tired. Do you see a squiggly, worm-like object in the sight picture? (Usually crosses your vision diagonally) The surface of your eye is starved for oxygen and you are watching a blood corpuscle go across the cornea of your eye. Relax, blink your eyes, and look at something else for a few seconds ... give your eyes a brief rest.

Step 4
As you may have noticed briefly at step # 3, your eye was going berserk trying to focus on the target, the front sight, and the rear sight all at the same time. You can't do it ... it's physically impossible for your eye to focus on three different objects at three different distances at the same time. Since the front sight determines where the bullet goes, focus on the front sight (fine tune it like your TV set so the front sight is sharp and clear). The target will get a little fuzzy and you will hardly see the rear sight for the blur (this is OK because it means you have focused on the front sight). Congratulations, you now have a perfect sight picture, using peep sights!

Shooting is a skill of consistency. IF you do everything the same way, every time you fire a shot ... you'll hit the bull's-eye every time (in theory at least). One more time, real quick on the four steps:
1 Find the blur
2 Put the front sight in the middle of the blur
3 Put the target at the tip of the front sight
4 FOCUS on the front sight"

- Koos Barnard's article in African expedition magazine on using them in the field:

http://africanxmag.com/ghost_rings.htm